This invention relates to an electronic musical instrument of a type which synthesizes a tone by a waveform generating operation such as a frequency modulation operation or an amplitude modulation operation. The invention relates more particularly to a synthesizer type electronic musical instrument which comprises a plurality of operation units (operators) for waveform generating operation and enables a performer to set a desired combination of input and output connection between these operation units.
A method or apparatus for synthesizing a tone of a desired tone color by a frequency modulation operation in audio frequency band or the like operation is disclosed in the specifications of U.S. Pat. No. 4,018,121 and Japanese Patent Preliminary Publication No. 7733/1980. For performing the tone synthesis by such frequency modulation operation more effectively, attempts are presently being made to employ a plurality of operation units and synthesize a tone of a predetermined tone color by suitably combining these operation units. In the prior art electronic musical instrument, however, the combination of the operation unit, i.e., algorithm of the frequency modulation operation, is previously set in correspondence to a specific tone color and the performer can only select a desired tone color by manipulating a tone color selection switch. The performer cannot set the combination of operation units, i.e., the algorithm of the frequency modulation operation as he desires but some algorithm of frequency modulation operation is selected within the musical instrument as a result of the manipulation of the tone selection switch. Besides, the prior art electronic musical instrument is directed not to selection of the algorithm of frequency modulation operation but to synthesis of a certain tone color and hence not many kinds of algorithms are provided but a mere switching operation between multinominal operation or multiplexing operation is performed.
In the field of electronic musical instruments, there are not only instruments of a type in which a present tone color is selected by a tone color selection switch but also instruments of a type, such as a music synthesizer, in which the performer can create a desired tone (tone color) by manipulating various switches and potentiometers. The latter type of instrument has an excellent characteristic in exploring musical possibility of the electronic musical instrument. The conventional musical synthesizer, however, is an analog control type apparatus employing a voltage and current control type circuit and there is limitation in the application of this system to a digital type electronic musical instrument employing the frequency modulation operation. It has therefore been desired to realize a synthesizer type instrument in the electronic musical instrument of the frequency modulation operation type in which the performer can synthesize any tone (tone color) as freely as he desires. This requirement exists not only in the frequency modulation operation type electronic musical instrument but also in an electronic musical instrument employing a tone synthesis system based on an amplitude modulation operation in the audio frequency band such as one disclosed in the specification of Japanese Patent Preliminary Publication No. 48720/1978.
It is, therefore, an object of the present invention to provide, in an electronic musical instrument of a type which synthesizes a tone by a modulation operation employing one or more phase signals or waveform signals in, for example, a frequency modulation operation or amplitude modulation operation, a synthesizer type electronic musical instrument according to which the performer can synthesize any tone (tone color) as freely as he desires.